1. Field of Invention
The present invention relates to a method for manufacturing a semiconductor device. More particularly, the present invention relates to a method for manufacturing a semiconductor device capable of solving junction leakage problem.
2. Description of Related Art
With the decreasing of the size of the integrated circuit and the increasing of the integration of the integrated circuit, the line width, junction area and junction depth are decreased. To effectively increase the functionalities of the device and to decrease the resistance and signal transmission delay due to the resistance and the capacitance, the metal silicide is formed at the junction region to effectively decrease the contact resistance.
In the well known self-aligned metal silicide manufacturing process, nickel silicide is formed at the surfaces of the gate, the spacer and the source/drain region of the metal-oxide semiconductor. However, nickel silicide possesses piping and spiking problems. That is, after the nickel silicide is formed, the nickel silicide diffuses into the substrate and the channel regions and the diffusion of the nickel silicide leads to current leakage. Therefore, to solve the problem mentioned above, a pre-amorphous implantation (PAI) process is commonly performed before the nickel silicide is formed so as to implant dopants including indium into the silicon substrate. Hence, the silicon surface is converted into an amorphous silicon structure. Therefore, the nickel piping and spiking phenomenon can be avoided.
Nevertheless, during the pre-amorphous implantation is performed, the end-of-range defect leads to a lot of defects generating at the surface of the source/drain region. Therefore, the junction leakage seriously happens at the source/drain region.